A Battle as Thin as a Strand or Two of Hair

In 1968, The seemingly insurmountable 10-second barrier in the 100m sprint was broken by James ‘Jim’ Ray Hines. He shattered a number that was considered the limit of human ability. The challenge of breaking limits continues in the world of watches as well.

Patek Philippe Grandmaster Chime Ref.5175 © watchesbysjx
/ Rolex Deepsea Challenge Ref. 126067 © Rolex

Topics such as the grand complication with the most functions or the diver’s watch that can go the deepest are always fascinating and a target for challenge. The quest to create the thinnest watch is no exception. This week’s topic is about the thinnest watches.

The Pinnacle of Ultra Slim

Ultra slim, Referring to the thinnest watches or movements, Is also called ultra thin, Extra thin, Or extra flat, But they all mean the same thing. In terms of pushing boundaries, Most other topics are about addition. More functions, Deeper water resistance (which physically makes the watch thicker), Longer power reserve, Higher price, And so on. The more you add, The more new records and limits are set. However, Ultra slim or the lightest watch is about subtraction. 

Jaeger-LeCoultre Master Ultra Thin 1907 © masterhorologer

The lightest watches are interesting due to new materials and variations in materials, But ultra slim is pure subtraction. The fewer the functions, The thinner the watch becomes. In the world of time-only watches with just hour, Minute, And second hands, It is common to remove the second hand to make the watch even thinner. Self-winding watches with rotors are thicker due to the rotor, So ultra slim watches are inevitably manual winding time-only models.

Dilemma

A very simple and static dial with only hour and minute hands. Manual winding, Which is losing market share due to convenience. The combination of the two is not assertive and does not easily gain popularity. Moreover, Ultra slim watches were almost always dress watches, Making them even less popular. That does not mean they are easy to manufacture. Even with the same functions, Making them thinner means lower durability and less tolerance between parts, Making assembly more difficult.

Patek Philippe Golden Ellipse (5.9mm) © teddybaldassarre

Audemars Piguet Royal Oak Selfwinding
Perpetual Calendar Ultra Thin (6.3mm) © teddybaldassarre

Ultra slim dress watches, Which required higher manufacturing costs and assembly skills but lacked a sense of movement, Were ultimately less popular. Because of this, Buyers had to pay a premium, And unless they understood the genre, It was not easy to open their wallets. Ultra slim, Which was once a quiet battleground for high-end brands like Patek Philippe, Audemars Piguet, Vacheron Constantin, Piaget, And Jaeger-LeCoultre, Faced a dilemma as it began to decline.

Vacheron Constantin Patrimony Contemporaine Ultra Thin
Caliber 1731 (8.09mm) © teddybaldassarre

Game Changer: Bulgari Octo Finissimo

It was Bulgari that reignited the ultra slim category in its decline. Not a traditional powerhouse in ultra slim, Bulgari boldly changed the rules of the game. Breaking away from the time-only manual winding formula, They released the thinnest watches in various complications such as chronograph, Tourbillon, And minute repeater, Continuously setting new records. These record-breaking achievements led to popularity, Allowing Bulgari to expand its presence. The main player was the Octo Finissimo.

Bulgari Octo Finissimo Tourbillon Automatic (1.95mm) / 
Bulgari Octo Finissimo Perpetual Calendar Platinum (5.80mm)
©hodinkee

With its octagonal motif and design emphasizing surfaces and angles, Inherited from Gerald Genta, It was the perfect form to express thinness. Thanks to this, Ultra slim became a genre of renewed interest, Attracting both traditional powerhouses and new challengers like Richard Mille, Turning the field into a hotbed of technical and creative competition.

Bulgari Octo Finissimo Ref. 102713 © bulgari

Although Bulgari broke the time-only manual winding formula and implemented ultra slim in various complications, The ultimate thinnest watch still had to be a time-only manual winding model. Bulgari could not avoid this to reach the pinnacle.

Octo Finissimo Ultra

Bulgari’s answer to the ultra slim of ultra slim was the Octo Finissimo Ultra (2022). For Bulgari, It was the eighth world record for the thinnest watch.

Bulgari Octo Finissimo Ultra (1.80mm)  © hodinkee

With a thickness of 1.80mm, The case is as thin as a 20 euro cent coin, Yet houses all the components needed for a mechanical watch. Extreme subtraction was applied to achieve this thickness. All components were spread out rather than stacked to avoid increasing thickness. As a result, The hour, Minute, And second hands are not on a single axis but are displayed on adjacent regulator dials (a type of reference clock used in watchmaking workshops, Characterized by separate displays for hour, Minute, And second hands).

Minute wheel subdial assembly © hodinkee

Major components are spread out to avoid overlapping as much as possible. The caseback also serves as the movement plate. Because the case is thin, Titanium and tungsten carbide were used to increase rigidity, And the sapphire crystal glass had to be processed as thin as paper. Normally, The crown is connected vertically to the case, But to reduce thickness, It was connected horizontally, With two crowns: one for time adjustment and one for winding. This broke away from the conventional framework and stereotypes of watches.

The Pinnacle of Ultra Slim

The Octo Finissimo Ultra seemed destined to reign as the thinnest watch for a long time, But in just a few months, It lost its throne to the Richard Mille UP-01 Ferrari.

RICHARD-MILLE RM UP-01 © ablogtowatch

The new king, At 1.75mm thick, Achieved ultra slimness using techniques similar to the Octo Finissimo Ultra, Even removing the crown and opting for a separate tool for operation. (This led many to call it cheating.) Because the ultra slim genre requires not only technical skill but also extraordinary patience, Many expected the Richard Mille UP-01 Ferrari to remain the thinnest watch, But it soon lost its title again.

Bulgari Octo Finissimo Ultra COSC © hodinkee

The enhanced version, Octo Finissimo Ultra COSC, Reclaimed the throne with a thickness of 1.70mm. It is 0.05mm thinner than its competitor and 0.1mm thinner than the Octo Finissimo Ultra. The secret, Unveiled in just two years, Was reworking the bezel and sapphire crystal glass. 

Thickness comparison between Octo Finissimo and Octo Finissimo Ultra COSC
© hodinkee

It is surprising that a 0.1mm reduction was achieved simply by reworking the case parts, Without altering the structure. It seems the case parts were pushed to their limit. Bulgari did not stop there and also obtained COSC certification. In fact, This is more impressive than the reduction in thickness. Achieving a daily accuracy of -4 to +6 seconds with such extreme thinness is a pinpoint balance between two nearly incompatible elements. The pinnacle of ultra slim may remain unshaken for now, But no one can be sure. Somewhere in Switzerland, Someone may be making a watch just a strand or two of hair thinner than the Octo Finissimo Ultra COSC.